Several patents and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents and publications is incorporated by reference herein.
Glass laminated products have contributed to society for almost a century. Beyond the well known, every day automotive safety glass used in windshields, laminated glass is used in all forms of the transportation industry. It is utilized as windows for trains, airplanes, ships, and nearly every other mode of transportation. Safety glass is characterized by high impact and penetration resistance and does not significantly scatter glass shards and debris when shattered.
Safety glass typically features a sandwich of two sheets or panels of glass bonded together with an interlayer of a polymeric sheet in between. One or both of the glass sheets may be replaced with optically clear rigid polymeric sheets, such as sheets of polycarbonate materials. Safety glass has further evolved to include multiple layers of glass and/or rigid polymeric sheets bonded together with interlayers of polymeric sheets.
The interlayer is typically made with a relatively thick polymer sheet, which exhibits toughness and bondability to provide adhesion to the glass in the event of a crack or crash. Over the years, a wide variety of polymeric interlayers have been developed to produce laminated products. In general, these polymeric interlayers must possess a combination of characteristics including very high optical clarity, low haze, high impact resistance, high penetration resistance, excellent ultraviolet light resistance, good long term thermal stability, excellent adhesion to glass and other rigid polymeric sheets, low ultraviolet light transmittance, low moisture absorption, high moisture resistance, and excellent long term weatherability, among other requirements. Widely used interlayer materials include complex, multicomponent compositions based on poly(vinyl butyral) (PVB), polyurethane (PU), polyvinylchloride (PVC), metallocene-catalyzed linear low density polyethylenes, ethylene-co-vinyl acetate (EVA), polymeric fatty acid polyamides, polyester resins, such as poly(ethylene terephthalate), silicone elastomers, epoxy resins, elastomeric polycarbonates, ethylene acid copolymers, ionomers and the like.
Architectural and automotive glazings are being constantly upgraded to withstand manmade and natural threats. Threat resistance may be demonstrated through many test protocols, such as the standards EN 12600, EN 1063 and EN 356 (European Committee for Standardization) in Europe for different impact types and assemblies of glass panels and interlayers. They define penetration resistance to impacting bodies with various levels of kinetic energy with defined glazing types. The most common test protocol is EN 356 P2A glazing, which involves a glass laminate consisting of two panels of 4 mm glass bonded by a 0.76 mm thick polymeric interlayer. Each of three (3) 1100 mm by 900 mm glass laminates with this construction is placed in a horizontal position to receive a 4.1 kg ball falling from a height of 3 m and the laminate is considered to have passed the test if no penetration is observed in any of the three (3) laminates tested.
A shortcoming of the interlayer sheets currently used in intrusion resistant glass laminates, which meet the EN 356 P2A standard, is that they typically possess a reduced glass adhesion, and therefore do not provide all of the safety aspects commonly associated with safety glass.
Solar cell modules or laminates, also referred to as photovoltaic modules, are units that convert light energy into electrical energy that can be useful for powering machinery, electrical equipment and appliances, for example. As a renewable energy resource, the use of solar cell modules is rapidly expanding.
In recent years, solar cell modules have become much more complex and demand enhanced functionality of the encapsulant materials incorporated therein. Encapsulant layers used in solar cell modules generally have requirements and compositions that are similar to those described above for glazing interlayers. For example, poly(vinyl butyral) compositions have commonly been disclosed as encapsulant layers for solar cell modules (see, e.g., U.S. Pat. Nos. 3,957,537; 4,249,958; 4,321,418; 5,508,205; 5,582,653; 5,728,230; 6,075,202; 6,288,323; 6,288,326; 6,538,192; 6,777,610; 6,822,157; 6,940,008, U.S. Patent Application Nos. 2004/0191422 and 2005/0284516, and European Patent Nos. EP 0 343 628, EP 0 631 328, EP 1 005 096, and EP 1 054 456).
Similarly, then, a shortcoming of the encapsulant materials used in solar cell modules is that they usually do not meet both the EN 356 P2A standard and the desired level of glass adhesion which is a safety aspect commonly associated with safety glass.
Conventional construction of a solar cell module features at least 5 structural layers. It is typically constructed in the following order starting from the top, or incident layer (that is, the layer first contacted by light) and continuing to the backing (the layer furthest removed from the incident layer): (1) incident layer; (2) front-sheet (first) encapsulant layer; (3) voltage-generating (solar cell) layer; (4) back-sheet (second) encapsulant layer; and (5) backing layer. The function of the incident layer is to provide a transparent protective window that will allow sunlight to be transmitted into the solar cell(s). The incident layer is typically a glass plate or a thin polymeric film (such as a fluoropolymer or polyester film), but could conceivably be any material that is transparent to sunlight. The encapsulant layers are designed to encapsulate and protect the fragile solar cell layer. Generally, a solar cell module will incorporate at least two encapsulant layers sandwiched around the solar cell layer. The optical properties of the front-sheet encapsulant layer must be such that light can be effectively transmitted to the solar cell layer.
The present invention overcomes these shortcomings by providing glazing interlayers and solar cell encapsulant layers tailored to provide improved intrusion resistance along with desired glass adhesion.